Fluorine-containing vinyl ether is a widely used polymer compound. Through copolymerization with other monomers for preparing fluoropolymers, it can prepare such materials as fluororesin, fluororubber, etc. that have special functions and are used under special conditions.
Fluorine-containing vinyl ether can be prepared from fluorine-containing acyl fluoride having a structure unit of
such as
etc. A lot of patents and literatures reported this preparation method, of which a literature indicated that the basic principle for preparing corresponding ether from fluorine-containing acyl fluoride is that perfluorinated acyl fluoride is at first reacted with salt-forming agent to generate perfluorinated carboxylate. Take sodium carbonate as an example, the salt-forming process thereof is:

Then the temperature is increased, the carboxylate is decomposed into CO2 and NaF, so as to prepare corresponding ether.
Currently, there are three main methods for preparing fluorine-containing vinyl ether:
First method: U.S. Pat. Nos. 3,321,532 and 3,291,843 disclose that in a nickel tube reactor, a nitrogen flow carries fluorine-containing acyl fluoride vapor to pass through a pipe loaded with metallic oxides (SiO2, CaO, ZnO, etc.), to prepare perfluorinated vinyl ether by cracking at a high temperature larger than 300° C. The maximum yield of the perfluorinated vinyl ether in the example reaches 95%, the preparation method thereof is simple and has a high yield.
Second method: U.S. Pat. Nos. 4,772,756, 4,554,112 and CN1520393A disclose that fluorine-containing acyl fluoride forms salt with K2CO3 or NaCO3 in the solvent, then cracks at the temperature of about 120° C. in the solvent, finally the perfluorinated vinyl ether which cracks from the solvent is obtained by evaporation. Such method controls the perfluorinated vinyl by the addition of N,N-dimethyl formamide to generate tetra-fluorinated ethyl ether containing hydrogen. The yield of these methods is further improved, and the yield can reach up to 96%.
Third method: U.S. Pat. No. 3,114,778 and CN101659602 disclose that acyl fluoride is neutralized with alkali to form fluorine-containing carboxylate, then dried and cracked at about 220° C. The perfluorinated vinyl ether prepared by such method has the lowest level of hydrogen-containing ether (which refers to fluorine-containing ether in which —O—CF═CF2 group is changed into —O—CFHCF3 group).
Generally, fluorine-containing acyl fluoride represented by general formula of
can be prepared by the addition reaction of fluorine-containing carbonyl compound
with hexafluoropropylene oxide in the presence of catalysis and solvent, wherein Rfy and Rfz may be —F or fluorine-containing alkyl. For example, U.S. Pat. No. 4,035,388 discloses a method for preparing fluorine-containing acyl fluoride by reacting fluorine-containing carbonyl compound with hexafluoropropylene oxide in dimethylamino difluorine phosphine and diglyme; U.S. Pat. No. 3,274,239 describes that fluorine-containing carbonyl compound reacts with hexafluoropropylene oxide in diethanol dimethyl ether with cesium fluoride as the catalyst to prepare fluorine-containing acyl fluoride; U.S. Pat. No. 3,250,808 provides a detailed description on self-aggregation of hexafluoropropylene oxide to prepare
meanwhile it also describes that some other fluorine-containing acyl fluoride are reacted with hexafluoropropylene oxide to generate corresponding
Thereby, fluorine-containing acyl fluoride having a structure unit of
can be obtained.